In recent years, an organic EL (Electro Luminescence) display device has been attracting attention as a thin, low-power consumption, high-speed response display device. The organic EL display device can be configured so that a screen is bendable at an arbitrary position, by using a plastic substrate or the like (see FIG. 14). Hereinafter, a display device having a bendable screen is referred to as a “flexible display device”.
For the flexible display device, the following techniques are known. Patent Document 1 describes a sensor device including a complementary type circuit shown in FIG. 15. In the complementary type circuit shown in FIG. 15, at least one of four transistors Tr1 to Tr4 is an organic TFT (Thin Film Transistor). Since an electrical characteristic of the organic TFT changes in accordance with a physical change, the organic TFT functions as a sensor element.
Patent document 2 describes a display device including a pixel circuit shown in FIG. 16. The pixel circuit shown in FIG. 16 includes complementary type transistors Tp, Tn as drive elements. When the screen is bent, characteristics of the transistors Tp, Tn change in opposite directions. Since a current flowing through one transistor increases and a current flowing through the other transistor decreases, fluctuation in a current can be suppressed for the entire pixel circuit.